The present invention relates to protecting polymerizable materials from interference from surrounding air during curing by providing a barrier over the curable material.
For many years it has been known that the oxygen in the air of the normal ambient environment interferes with the curing of polymerizable materials by what is reported as oxygen inhibition. By this it is understood that the oxygen present in the air retards or even prevents the polymerization of the compositions and particularly at their surface interface with the air. In general, the surfaces of unprotected surfaces remain tacky because of incomplete polymerization of the resins and the surface remains weak and subject to leeching and other deleterious action.
U.S. Pat. No. 3,458,311 reveals a photopolymerizable stratum that is protected by an adherent solid protective stratum present in an amount of 2 to 30 mg/dm.sup.2 made from a mixture of hydrophilic water soluble polymers such as those shown in Column 2 including polyvinyl pyrrolidone and polyvinyl alcohol and a surfactant in water. Optionally a chain transfer agent may by present as taught in Column 2 Line 32.
U.S. Pat. No. 4,072,528 also reveals a photopolymerizable element having a support and in addition a polymerizable photosensitive layer on the support and a solid water permeable oxygen barrier protective layer over the polymerizable photosensitive layer. The protective layer is applied as a coating from an aqueous solution of a water soluble macromolecular organic copolymer such as polyvinyl alcohol having disbursed therein finely divided solid particles of a water insoluble chlorinated vinyl copolymer.
It is an object of the present invention to provide a surface cure promoting coating that overcomes the deficiencies of the prior art.
It is a further object of the present invention to provide a curing of polymerizable compositions that is adequate to withstand use in long term application in the oral environment of the human mouth.
By yet another object of the present invention it is desired to provide a rapid rate of cure to a substantial depth and at the same time provide a surface that is non-tacky and resistant to acids and bases; and resistant to staining, fouling, odor sorption and blanching and has good durability or weatherability and a glossy surface.
An additional object of the invention is to provide a liquid composition that enables vertical surfaces to be coated with a substantially thick coating that is fluid enough to assure an uninterrupted non-leaking surface.
Another object of the invention is to use a material that will not cause a toxic end product.
Another object of the invention is to provide an economical method of curing polymerizable materials.